DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0024] Referring now to FIG. 1, there is shown a closed pressure system 10 of the prior art. By way of example, pressurized air is contained in a closed tubing 12 to be released for applications such as providing power to drive tools, lifts and even to burn waste oil. For waste oil applications it is desirable that the pressure be maintained above a low pressure side for twenty four hours per day. In one non-limiting example, the pressure of the air is maintained at 175 pounds per square inch on the high side, hereinafter high pressure threshold, and 145 pounds per square inch on the low side, hereinafter low pressure threshold.

[0025] Once the air pressure of the system 10 falls to the low pressure threshold a compressor 14 driven by a motor 16 raises the air pressure of the system 10 until the high pressure threshold is reached. The motor 16 is powered by two hundred and twenty volts of single phase power carried along wires 18 and 20.

[0026] A pneumatic controller 22 closes a first contact 24 and a second contact 26 at the low pressure threshold, thereby allowing electric current to power the motor 16. The current powers the motor 16 until the compressor 14 raises the system pressure to the high pressure threshold.

[0027] At the high pressure threshold, the pneumatic controller 22 opens the first and second contacts 24 and 26 to cut the electric current to the motor 16. The system 10 now discharges pressure through normal use until the low pressure threshold is once again reached.

[0028] One problem inherent in this system 10 occurs when a rupture arises in the closed tubing 12. The pressure of the system 10 now falls to the low pressure threshold, but it is impossible to return to the high pressure threshold due to the leak. As a result, the motor 16 continues to run indefinitely until it is manually turned off. Failure to manually turn off the motor 16 in time causes the motor 16 to overheat which invariably destroys the motor 16. Overheating the motor 16 can also cause a fire which can destroy an entire facility.

[0029] In some situations, a heater coil 27 senses the temperature of the motor 16 and stops electric current from reaching the motor 16 when the motor 16 becomes too hot. However, at this point the compressor 14 and the motor 16 are invariably damaged.

[0030] Turning now to the present invention which will be described in accordance with a closed pressure system 17 depicted in FIG. 2, the closed tubing 12 contains pressurized air which is to be released for applications such as providing power to garage type tools (not shown) or for keeping primed a well pump (not shown).

[0031] As described above the motor 16 drives the compressor 14 to charge the system from the low pressure threshold to the high pressure threshold. Two hundred and twenty volts of electric current provides power to the motor 16 through conductors 18 and 20 each carrying one hundred and ten volts. Yet again as described above the pneumatic controller 22 closes and opens the first and second contactors 24 and 26 to power and cut power to the motor 16.

[0032] To prevent the motor 16 from running indefinitely a timing relay device 30 is electrically connected between the power source 25 and the motor 16. In FIG. 2, the timing relay device 30 includes an internal relay (not shown) that breaks conductor 18 before first contactor 24. In an alternative embodiment depicted in FIG. 5, the timing relay device breaks conductor 18 after first contactor 24.

[0033] The timing relay 30, externally powered through connector 37, operates by tracking time and then performing a certain function when a predetermined set run time is reached. The timing relay 30 includes an internal timer and actuator (not shown) that are connected across either contactor 24, 26 or an auxiliary contactor not shown. The internal timer continuously accumulates time until electric power to it is discontinued, at which point the accumulated time resets to zero. The actuator opens the internal relay upon reaching the set run time, which cuts electric power to the motor 16.

[0034] A toggle switch 32 is electrically inserted into the system 17 so that it allows current to bypass the timing relay device 30 when the toggle switch 32 is in the untimed (ON) state. The toggle switch 32 is designed so that it operates at one of two states (ON/OFF) until it is changed. The user sets the toggle switch 32 for either a timed or untimed (bypass) run. Obviously, the toggle switch 32 is initially set to the timed (OFF) state so that the timing relay device 30 is operable.

[0035] In other words, the timing relay 30 in concert with the toggle switch 32 acts as a safety cutoff for the motor 16 having bypass capability. This prevents destruction of the motor 16 in case of a system leak or a fire if the motor 16 overheats because of non-stop running.

[0036] Normally it takes the motor 16 a predetermined amount of time to force the compressor 14 to charge the system 10 from the low pressure threshold to the high pressure threshold. Therefore, the timing relay 30 set run time must be greater than amount of time it takes the motor 16 and compressor 14 to complete a single charging cycle from low pressure threshold to high pressure threshold with an operable system 10.

[0037] At the high pressure threshold the pneumatic controller 22 opens the contactors 24, 26 thereby stopping the flow of electric current through the system 17. As a result, the relay timer 30 resets itself to zero time.

[0038] According to the diagram depicted in FIG. 2, when the toggle switch 32 is closed, electric current bypasses the timing relay 30 thus forcing the system 17 to operate in accordance with the prior art.

[0039] When the toggle switch 32 is open, the electric current flows through the timing relay 30 thus gaining the above described features, functions and advantages of the present invention.

[0040] In operation and according to a preferred embodiment, the invention shall now be described with reference to FIG. 3. Considering a system 10 charged to the high pressure threshold of 175 pounds per cubic inch, the pneumatic controller 22 forces open the contacts 24 and 26. Consequently, no power is provided to the relay timer 30 thereby initializing the relay timer 30 to zero time, shown in step 40.

[0041] As the system 10 operates the pressure gradually decreases to the low pressure threshold of 145 pounds per cubic inch. At this system pressure, the pneumatic controller 22 forces contacts 24 and 26 closed, shown in steps 42 and 44. The relay timer 30 begins counting time, shown in step 46. The motor 16 and compressor 14 are now charging the pressure within the system 17.

[0042] Now two competing interests unfold. In a properly working system 17 with no ruptures, the system pressure will reach the high pressure threshold, step 48, before the set run time is reached, step 52. In one practical example, it takes the system 17 approximately two and a half minutes to charge to the high pressure threshold. Therefore, the predetermined amount of time is set for four minutes.

[0043] If the system 17 is working properly, then upon reaching the high pressure threshold the pneumatic controller 22 forces the contactors 24 and 26 open, shown in step 50. Thus, the relay timer 30 is initialized to zero time as depicted in step 40.

[0044] In a ruptured or leaky system 17, the high pressure threshold will never be attained upon charging. As a result, the predetermined amount of time will be reached before completely charging the system 17, shown in step 52. At this point, the relay timer 30 forces open a pair of internal relays thereby cutting power to the motor 16, shown in step 54.

[0045] The contacts 24 and 26 are still closed because the high pressure threshold was never attained. In certain circumstances it may be desirable to run the motor 16 longer than the set run time. For example, in sandblasting applications it is desirable to run the motor 16 for fifteen continuous minutes. The user simply forces the toggle switch 32 to the untimed (ON) state to override the relay timer 30. As a result, the motor 16 runs continuously with the toggle switch 32 acting as an override switch.

[0046] The relay timer 30 activates an alarm 36 when the set run time is reached, shown in step 56. The alarm could be any type of audio or video alarm.

[0047] FIG. 4 depicts a housing faceplate 60 for the closed pressure system 17. The toggle switch 32 disposed through the faceplate 60 gives the user convenience access to set either a timed or a bypass run as previously described. A reset button 62 allows the timing relay 30 to be automatically reset.

[0048] An alert indicator 64 illuminates when the pressure system 17 fails or “times out.” A normal indicator 66 illuminates when the system 17 is in normal use. Finally, a bypass indicator 68 illuminates when the toggle switch is set to bypass or “override.”

[0049] Various changes and modifications, other than those described above in the preferred embodiment of the invention described herein will be apparent to those skilled in the art. While the invention has been described with respect to certain preferred embodiments and exemplifications, it is not intended to limit the scope of the invention thereby, but solely by the claims appended hereto.